The number of elderly Medicare beneficiaries enrolled in managed care plans has grown rapidly in the past few years, and recent changes in Medicare are likely accelerate this trend. Because managed cre plans use financial incentives and non-financial mechanisms to curb utilization, there is concern that the elderly in these plans may face barriers to receiving appropriate medical care. This concern is especially acute with respect to elderly persons of low socioeconomic status. Despite widespread interest in the impact of managed care on the use of medical services by vulnerable elderly populations, there is currently little research on this issue. The propose project is a 3-year observation study of the influence of socioeconomic status (SES) on the medical care utilization of elderly Medicare beneficiaries enrolled in HMOs, and represent a collaborative effort between investigators at RAND and the Center for Health Care Policy and Evaluation at United Health Care, a leading managed care organization. The goals of the project are to evaluate the impact of SES on: 1. total physician visits, visits to primary care physicians, and visits to specialists; 2. visits to non-physician providers; 3. hospitalization rates and hospital length of stay; 4. use of the emergency room as a source of care; 5. rates of mammography and influenza vaccination; 6. total charges for medical care. A secondary goal of the project is to provide information on the pathways by which SES affects utilization among elders in managed care plans. This project will assess the utilization experience of enrollees in 3 geographically dispersed Medicare HMOs that are affiliated with UHC. Data sources will include a telephone survey of enrollees and administrative data from the study HMOs. To identify the effect of SES on utilization, we will estimate multi-variate regression models that control for comprehensive measures of health status and other factors that may affect the demand for medical care. The results of this project will provide important new information to policy makers and directors of health care plans on how well elderly persons of low SES fare in managed health care systems designed to control utilization. These understudied questions are particularly important to address given the increasing numbers of Medicare beneficiaries who will receive their medical care in managed care settings.